Does it make more sense to heavily customize an application, or build from scratch? We help you with the estimate.

When NASA started using off-the-shelf modems as a low-cost way to help its probes phone home, other government agencies sat up and took notice. They weren't really surprised the modems worked; they were surprised that nasa had the gumption (or desperation) to get off-the-shelf components through the Byzantine federal acquisitions process.

Using a $50 modem instead of a custom-designed, vacuum-tested, military-spec'd computer modulation/demodulation data transmission element was something of a departure. The feds even needed a new acronym: COTSs, for commercial off-the-shelf technology.

Corporate information-technology managers are much more used to ordering up commercial software, but not always accustomed to the idea of using off-the-shelf programs as components for their own customized applications. So says Arlene Minkewicz, chief scientist at Price Systems, a consultancy specializing in the cost control of large information-technology projects.

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The biggest advantage of COTS development—buying and then customizing commercial software—is that other people do most of the design, programming, testing and bug-fixing for you, Minkewicz says. "You don't have to keep those software development resources on hand," she explains.

COTS does not make sense for highly specialized applications, but any software with functions common to many organizations is a good candidate.

One thing to watch out for is integration costs, which can skyrocket if you lose the balance between what the store-bought software can do for you and what is cheaper to do yourself.